Sample analysis by analyzing the components contained in a sample such as urine or blood collected from a living body is widely performed in the field of clinical examinations, and sample analyzers that automate the sample analysis process have come into use in recent years.
U.S. Patent Publication No. 2009/091746 discloses a cell analyzer that analyzes cells by the flow cytometry method. The cell analyzer causes a measurement sample containing stained nucleic acid to flow through a flow cell and which is irradiated by laser light that forms a beam spot that is 3 to 8 μm in diameter in the flow direction of the measurement sample flowing through the flow cell, and uses the pulse area (integral value) of the resulting fluorescent light signal to classify cells with a nucleus 10 to 15 μm in size as abnormal cells, and classify cell with a nucleus 5 to 7 μm in size as normal cells.
Urine and body fluids may contain small cells such as bacteria in addition to white blood cells, epithelial cells, and atypical cells which are relatively larger. For example, white blood cells have a diameter of approximately 10 to 15 μm, and the diameter of the nucleus is about 10 μm. In contrast, the diameter of a bacterium is only approximately 0.4 to 2 μm. That is, a bacterium is much smaller than the nucleus of a white blood cell.
Although the cell analyzer disclosed in U.S. Patent Publication No. 2009/091746 is suitable for analyzing body fluids which contain large cells, it is unsuitable for analyzing samples which contain cells in a broad range of sizes from large cells to small cells as in the case of urine and body fluids.
It is desired to accurately analyze samples such as urine and body fluids which contain cells in a broad range of sizes from large cells to small cells.